The present invention relates to a process for preparing free alkylphenol flavor concentrates. For the purpose of this invention free alkylphenol flavor concentrates are defined as free alkylphenol solutions resulting from the treatment of a naturally-occurring source of bound alkylphenol conjugates. Such concentrates and synthetic alkylphenols are used as additives in various food products for the enhancement of food flavors and food appearance. For the purpose of this invention alkylphenols are defined as phenols substituted with one or more saturated or unsaturated alkyl groups, where the groups can be the same or different. Alkylphenols are naturally produced in the digestive systems of dairy and meat animals, and are thus present in various food products, such as meats (Ha, J. K. and Lindsay, R. C. Volatile Alkylphenols and Thiophenol in Species-Related Characterizing Flavors of Red Meats, J. Food Sci. 56:1197 (1991) (incorporated herein by reference)); milks and cheeses (Ha, J. K. and Lindsay, R. C. Volatile Branched-Chain Fatty Acids and Phenolic Compounds in Aged Italian Cheese Flavors, J. Food Sci. 56:1241 (1991); Ha, J. K. and Lindsay, R. C. Contributions of Cow, Sheep and Goat Milks to Characterizing Branched-Chain Fatty Acids and Phenolic Flavors in Varietal Cheeses, J. Dairy Sci. 74:3267 (1991) (incorporated herein by reference)); cashews (Tyman, J. H. P. et al. The Extraction of Natural Cashew Nut-Shell Liquid from the Cashew Nut (Anacardium occidentale), J. Am. Oil Chem. Soc. 66:553 (1989)); and off-flavored fish (Heil, T. P. and Lindsay, R. C. A Method for Quantitative Analysis of Flavor-Tainting Alkylphenols and Aromatic Thiols in Fish, Environ. Sci. Health. B23:475-88 (1988) (incorporated herein by reference)). For example, various aged Italian cheeses contain many volatile, or xe2x80x9cfreexe2x80x9d alkylphenols in concentrations ranging from 1 part per billion (xe2x80x9cppbxe2x80x9d) to 924 ppb, but the specific alkylphenols present, as well as their concentration, vary from cheese to cheese. (Ha, J. K. and Lindsay, R. C. Volatile Branched-Chain Fatty Acids and Phenolic Compounds in Aged Italian Cheese Flavors. J. Food Sci. 56:1241 (1991) (incorporated herein by reference)). P-cresol and m-cresol have also been found in butter oil at a concentration of 4.9 ppb and 3.3 ppb respectively. (Urbach et al., Die Isolierung und Bestimung von Phenol, o-Methoxyphenol und m-und p-Cresol in Butter, 18th Int. Dairy Congr., Sydney IE, 234 (1970)).
Alkylphenols have been identified as important components in the flavors of ruminant meats and dairy products. For the purpose of this invention, ruminant is defined as relating to a multiple-stomached animal, such as bovine, caprine and ovine. Alkylphenols are present in both the free and conjugate-bound forms, but only the free forms contribute to the flavor of the product. Alkylphenols are very potent flavor compounds, providing noticeable flavor at low parts per billion concentrations. Studies by Urbach showed that the addition of 2 ppb of p-cresol and 200 ppb of m-cresol to a model butter prepared from deodorized butter oil and distilled water, produced desirable flavor notes, but that undesirable flavors in the butter resulted from the use of p-cresol and m-cresol in amounts greater than 100 ppb and 1 part per million (xe2x80x9cppmxe2x80x9d) respectively. (Urbach et al., Volatile Compounds in Butter Oil, J. Dairy Res. 39:35 (1972)).
The free alkylphenols found in dairy products, such as milk, and in animal tissue are generally highly soluble in fats, such that when fats are removed from these products, the free alkylphenols are also substantially removed. As a result, such xe2x80x9cfat freexe2x80x9d products do not have the flavor of their fat-containing counterparts, making them less desirable to consumers.
The flavorful free alkylphenols naturally found in meat and dairy products are produced in the digestive tract via normal processes and/or via ingestion of feeds containing alkylphenols. However, most of the alkylphenols found in milk, urine and animal tissue are metabolic conjugates, such as glucuronides, sulfates, and phosphates, which are not believed to have much, if any, flavor effect. Therefore, lab-scale methods have been developed to produce free alkylphenols from these alkylphenol conjugates, including enzyme hydrolysis using xcex2-D glucuronidase, arylsulfatase, and acid phosphatase, simultaneous distillation extraction and adsorption.
Moreover, despite the fact that free alkylphenols are recognized as contributing flavors to food products, to date these compounds have not been used as flavor enhancers in the food industry because usefulness of the free alkylphenols as flavor enhancers for xe2x80x9cfat freexe2x80x9d or xe2x80x9creduced fatxe2x80x9d products has not yet been recognized. In addition, the above processes for isolating free alkylphenols from food products such as milk and animal tissue are difficult, expensive and time consuming, and have only been accomplished on a small scale.
Therefore, a process for producing free alkylphenol flavor concentrates from raw materials containing bound alkylphenol conjugates that is efficient, simple, inexpensive, and that can be performed on a large scale is needed. A process for using these free alkylphenol flavor concentrates as flavor enhancers in food products, especially xe2x80x9cfat freexe2x80x9d or xe2x80x9creduced fatxe2x80x9d products, is also needed. A process for using synthetic alkylphenols as flavor enhancers in food products, especially xe2x80x9cfat freexe2x80x9d or xe2x80x9creduced fatxe2x80x9d products, is also needed. A xe2x80x9cfat freexe2x80x9d or xe2x80x9creduced fatxe2x80x9d food product with a flavor substantially matching that of its counterpart wherein the fat has not been removed is needed. Further, there is a need for a free alkylphenol flavor concentrate that can enhance the appearance of food products and be applied in a controlled manner to impact flavor and color in desired locations in or on the food product.
These needs are met by the present invention.
A process for producing free alkylphenols from raw materials containing bound alkylphenol conjugates and the subsequent recovery of the free alkylphenols as a free alkylphenol flavor and color concentrate has been discovered. In addition, applications of free alkylphenols, both in synthetic form and as a free alkylphenol flavor concentrate derived from the above process, as flavor enhancers in various food products have been discovered. The release of the bound alkylphenols from their non-flavorful conjugates provides the active flavorful compounds that are present in dairy and ruminant meat products in low concentrations. These free alkylphenols, when added in the appropriate amounts to food products provide the characteristic flavors of these foods. Therefore, even xe2x80x9cfat freexe2x80x9d or xe2x80x9creduced fatxe2x80x9d food products will have a flavor substantially matching that of their counterparts wherein the fat has not been removed.
In the process of the present invention, the free alkylphenols are released from their bound form by reacting raw materials containing bound alkylphenol conjugates with a strong acid, such as sulfuric acid, phosphoric acid or hydrochloric acid, mineral to effect hydrolysis of the alkylphenol conjugates. Preferably, a reacting time period is used to cause sufficient degradation and/or polymerization of interfering flavors, proteins and carbohydrates present in the raw material to avoid sweet molasses-like flavor notes. The sufficient time period is normally about one to about eight hours. The resulting hydrolyzed free alkylphenol flavor concentrates may be partially neutralized with a base, such as sodium hydroxide, sodium carbonate, ammonium hydroxide, sodium bicarbonate, potassium hydroxide or potassium carbonate, if desired.
The free alkylphenol flavor concentrates should then be analyzed to determine the profile, or types and concentration of free alkylphenols present in the concentrate. It is essential to control the concentration of alkylphenols that are added via the free alkylphenol flavor concentrates, and to do this, the concentration of alkyphenols in the free alkylphenol flavor concentrates must be known. Various analytical techniques can be used to determine the profile, such as high performance liquid chromatography (HPLC), gas chromatography (GC) and extraction. This profile, which will vary depending on the raw material to used in the process and even within different batches of the same type of raw material, allows the user to determine the amount of free alkylphenol flavor concentrate to be added to a given food product to produce a food product having a taste that is pleasing to consumers.
The free alkylphenol flavor concentrates of the present invention are stable for an indefinite amount of time and small additions in the parts per billion concentration range are used to impart dairy or meat flavors or a richness to applications including meats; dairy products, such as butter, milks, aged cheese, cream cheese, ice milks, etc.; chocolate products; soy-product meat substitutes; baked, fried or microwaved goods; animal foods; and many others. The free alkylphenol flavor concentrates of the present invention are particularly useful in xe2x80x9cfat freexe2x80x9d or xe2x80x9creduced fatxe2x80x9d food products. Other flavors may be combined with the free alkylphenol flavor concentrates to provide more complete natural flavors.
Synthetic alkylphenols, either individually or in combination, may be used to provide the same flavor effects as the natural alkyiphenols without the addition of fat. Among the alkylphenols useful in this application are p-cresol, m-cresol, p-ethylphenol, m-ethylphenol, and m-propylphenol.
Since the presence of these metabolic conjugates and corresponding free compounds in milk, meat, poultry, fish, and seafoods depends on the amount of metabolic conjugates ingested by the animal and the natural metabolic processes of the animal, considerable variation in the concentrations will be found in these foods. Thus, feeding and culturing practices greatly affect the flavor potential of resulting food products, and intensive production and culturing practices often result in alteration of traditional flavors associated with milk, meat, poultry, fish, and seafood products.
Further objects, features and advantages of the invention will be apparent from the following detailed description.
One process of the present invention for preparing free alkylphenol flavor concentrates includes reacting a raw material containing bound alkylphenol conjugates and a strong acid in an aqueous solution to hydrolyze the alkylphenol conjugates into their free alkylphenol counterparts. The reaction should proceed for a period of time sufficient to effect hydrolysis of the bound alkylphenol conjugates to the free alkylphenols, generally this process takes at least about one hour. However, the amount of time necessary to effect sufficient hydrolysis is dependent upon the pH of the solution and the temperature, if any, to which the solution is heated. The amount of time necessary to effect sufficient hydrolysis is also dependent on the raw material used. For example, the concentration of alkylphenols varies from one raw material to the next and from one batch of the same type of raw material to the next. Also, the buffering capacities of the raw materials vary. Thus, the reaction time will vary depending upon the raw material used and the desired resultant concentration of free alkylphenol.
A preferred aqueous raw material solution should contain sufficient strong acid to achieve a pH of from about 1 to about 4, and more preferably, the pH should be from 1 to about 3. Although the solution does not need to be heated, preferably, the solution should be heated to a temperature of at least 50xc2x0 C. Most preferably, the temperature should be from about 90xc2x0 C. to about 121xc2x0 C.
It is also preferred that the raw material solution containing bound alkylphenol conjugates is heated for an amount of time sufficient to both (1) hydrolyze a substantial amount of the alkylphenol conjugates in the solution to their free alkylphenol counterparts, and (2) cause the degradation and/or polymerization of interfering flavor compounds, proteins and carbohydrates in the raw material so that they do not contribute masking or distorting sweet, molasses-like flavor notes to the resulting concentrate. Preferably, the raw material is heated with a strong acid for about one to about eight hours. Again, however, the optimum time needed to achieve both effects is dependent upon the pH and temperature of the solution, and can be readily determined. The hydrolyzed free alkylphenol flavor concentrates may be partially neutralized with a base, if desired.
Raw materials that can be used in the process of the claimed invention include, but are not limited to, ruminant milk, buttermilk, whey, whey permeate, delactosed whey permeate, cashews, and ruminant urine, all of which contain bound alkylphenol conjugates.
The most preferred raw material is delactosed whey permeate, which is essentially a waste product from the production of whey protein ingredients and lactose. This raw material is preferred because it contains a high concentration of bound alkylphenol conjugates and is inexpensive. Different whey permeates have different bound alkylphenol conjugate profiles, and therefore, will result in different free alkylphenol flavor concentrates.
The strong acid can be any of the generally known strong acids, including mineral acids, such as sulfuric acid, phosphoric acid or hydrochloric acid. Preferably, the strong acid is sulfuric acid, phosphoric acid or hydrochloric acid. Preferably, sufficient strong acid should be added to achieve a pH of from about 1 to about 3 and a concentration of about 0.5 Normal to about 5 Normal.
The solution is preferably reacted for a time sufficient to form a free alkylphenol concentrate having a free alkylphenol concentration of at least about 500 ppb of p/m-cresol. Most preferably, the free alkylphenol concentration is at least about 2000 ppb of p/m-cresol.
After the solution has been reacted to hydrolyze a sufficient amount of the bound alkylphenol conjugates, and preferably, to cause the degradation and/or polymerization of a substantial amount of the interfering flavor compounds, proteins and carbohydrates in the raw material, the resulting free alkylphenol flavor concentrate can be neutralized with base. The free alkylphenol flavor concentrate is preferably neutralized just prior to use in an application where the acidic nature of the concentrate may present difficulties in the processing. While any base can be used, the preferred base is sodium hydroxide. Preferably, the base is added in sufficient quantity to produce a pH of from about 3.5 to about 5.
The free alkylphenol flavor concentrate is stable for an indefinite period of time at a pH less than or equal to about 3 and under either refrigerated or ambient conditions.
The free alkylphenol flavor concentrate obtained via the above-described process should next be analyzed to determine its xe2x80x9cprofile,xe2x80x9d or the specific types and concentrations of free alkylphenols present in the concentrate. Such analysis is important, because free alkylphenol flavor concentrates obtained from different raw materials, and even different batches of the same type of raw material will have different profiles. Moreover, to most accurately determine the proper amount of concentrate to be added to a given food product to achieve a given flavor consistency is required and it is desirable to know the concentrate profile.
The profile of the free alkylphenol flavor concentrate can be obtained via various analytical techniques, including HPLC, GC or extraction. Use of HPLC is preferred. It is essential to control the concentration of alkylphenols that are added via the free alkylphenol flavor concentrates, and to do this, the concentration of alkyphenols in the free alkylphenol flavor concentrates must be known. A rapid high performance liquid chromatography analysis procedure may be used for this purpose. Generally, free alkylphenols are extracted either on-line in the process or from an end product sample, and then are analyzed by fluorescence detection using precolumn derivatization with dansyl chloride. When analysis of total alkylphenols (free+conjugate-bound) is desired, the extracted conjugates are first hydrolyzed by a combination of enzyme and acid hydrolysis before derivatization. The detection limit of dansylated alkylphenols by this procedure is about 0.2 nanogram absolute amount. Calibration curves are linear for dansylated alkylphenols from the detection limit to about 60 nanograms for phenols and cresols injected, and 80 nanograms for other alkylphenols injected, and overall the correlation coefficient between added and recovered alkylphenols is 0.98 or higher. The internal standard utilized is o-cresol. The concentration of p/m-cresol in the sample is determined from the area under the curve using standard techniques. The total concentration of alkylphenols in the free alkylphenol flavor concentrate is based upon the concentration of p/m-cresol in the free alkylphenol flavor concentrate. (Zeng, Q. Influence of Milkfat on the Formation of Flavor Compounds in Cheddar Cheese. Ph.D. diss. University of Wisconsin-Madison (1997) (incorporated herein by reference).)